The present invention relates to a toroidal continuously variable transmission (CVT) having an improved structure of supporting power rollers which serves for enhancing assembly efficiency of the toroidal CVT, and a method of assembling the toroidal CVT with the power rollers supporting structure.
Generally, toroidal CVTs have input and output disks arranged to be rotatable about a common rotation axis, and a plurality of power rollers interposed between the input and output disks in contact therewith via a working fluid (traction oil). These power rollers are supported on trunnions so as to rotate about rotation axes and pivotally move about pivot axes perpendicular to the rotation axes thereof. Upon operating the toroidal CVTs, the power rollers are pressed by the input and output disks undergoing a load corresponding to a transmission torque. A shear force of the working fluid is caused corresponding to the pressing force applied to the power rollers. Owing to the shear force, the power rollers transmit power between the input and output disks. The power rollers, therefore, tend to be pushed out from a toroidal cavity formed between the input and output disks. In order to avoid the push-out of the power rollers, opposed end portions of each trunnion supporting the power roller are connected with those of the adjacent trunnion via links, respectively. Upon the speed change operation of the toroidal CVT, the respective trunnions are driven by a servo piston to synchronously displace or offset from the non-speed change position where the rotation axes of the power rollers are perpendicular to the common rotation axis of the input and output disks, along a direction of the pivot axes of the power rollers at the identical stroke. In this condition, the trunnions with the power rollers are allowed to pivotally move about the pivot axes due to component of force of the rotation of the input disk.
U.S. Pat. No. 5,893,815 (corresponding to Japanese Patent Application First Publication No. 9-317837) discloses a toroidal CVT including a link which is swingably supported on a transmission case via link posts and pins. Each pin is fixed to the link and swingably engaged in a hole of the link post. Upon assembling the toroidal CVT, the link posts are preassembled to the link using the pins, and then the preassembled link posts are fixed to the transmission case. Thus, the link is swingably mounted to the transmission case so as to permit the above-described offset motion of the trunnions in the direction of the pivot axes.
United States Patent Application Publication No. US 2001/0016534 A1 (corresponding to Japanese Patent Application First Publication No. 2001-182793) discloses a toroidal CVT including a link which connects a pair of front trunnions and a pair of rear trunnions with each other. The link is swingably supported on a transmission case via link supports and pins. The pins are fixed to the link supports and engaged in oval holes of the link which are elongated in a direction of pivot axes of power rollers supported on the respective front and rear trunnions, but are not open to an outer periphery of the link. This permits the link to swingably move along the direction of the pivot axes. Even when one of each pair of trunnions interferes with the link during the offset motion thereof, the other of the each pair of trunnions can be free from the interference force that will be exerted on the other via the pins acting as a fulcrum. If the interference force is exerted on the other, distribution of the torque to the power rollers on the front and rear trunnions will be deteriorated. Upon assembling the toroidal CVT, the link supports with the pins are preassembled to the link by inserting the pins into the elongated holes. The preassembled link supports then are mounted to the transmission case, so that the link is swingably supported on the transmission case.